1. Field of the Invention
The present invention relates to an information storage medium on which land tracks and groove tracks are alternately formed every round. The present invention also relates to an information reproduction method for reproducing information from such an information storage medium. Furthermore, the present invention relates to an information recording method for recording information on such an information storage medium.
2. Description of the Related Art
As is well known, in recent years, single-sided/single-layered optical disks having a capacity of 4.7 GB have been put into practical use. For example, rewritable DVD+RW, DVD-RW, and DVD-RAM disks are known. An information recording layer is formed on a transparent substrate of each of these optical disks, and land tracks and groove tracks are alternately formed every round on this information recording layer. Information is recorded on/reproduced from an optical disk along these tracks. That is, by focusing a laser beam on these tracks, information is recorded on these tracks and information recorded on these tracks is reproduced.
Of the aforementioned optical disks, a DVD-RAM records a physical address used to specify a spatial position where information is to be recorded/reproduced. For example, this physical address is formed to interrupt tracks, and is called a complementary allocated pit address (CAPA). A track jump action is allowed within a region where this CAPA is recorded.
In contrast, on a DVD+RW, a physical address is reflected on each groove track by utilizing groove wobble modulation (to be referred to as wobble modulation hereinafter) that slightly wobbles each groove track in the radial direction. This method changes the phase of wobbles in correspondence with information (physical address) to be recorded, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-283738. The physical address recorded by such wobble modulation does not interrupt the recording tracks. That is, the physical address recorded by the wobble modulation does not squeeze the recording area of user information on the disk. For this reason, high format efficiency and high compatibility with read-only media can be assured.
On the aforementioned optical disk having tracks with the land & groove structure, the depth from the disk surface to the land track is different from that to the groove track. Hence, the servo polarity for the land track and that for the groove track must be switched.
Since the servo polarities must be switched, access to a target address by a jump may often become inefficient.